You'll get a better appreciation of the task if you go to Gumpydog's site and look at the pictures. The airbeams are rectangular tubes about 6x6 or 6x8 and 36-40" long buried in the frame structure below the floor and inside the wheels.

It can be done - anything can if you're determined enough! but it's alot of work. My "California" MCI-9 had a huge amount of fine silt all over this area that served as a "sponge" making sure the corrosion continued long after the rain was gone. Haven't "tested" for leaks yet, but I'll let you know if any show and what I do to address the problem.